ICAD: TBI History Doubles Dementia Risk in Vets

Action Points

Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Note that in this study, a history of prior traumatic head injury of any type was associated with a significant increase in the risk of subsequent dementia.

PARIS -- Older veterans who had suffered a traumatic brain injury (TBI) in the past -- in combat or not -- were twice as likely to have a subsequent diagnosis of dementia as vets without a history of such injuries, it was reported here.

Nearly 16% of veterans 55 and older whose medical records indicated a TBI at some point had received a diagnosis of dementia, compared with 6.8% among non-TBI veterans (P<0.05), according to Kristine Yaffe, MD, of the University of California San Francisco.

Dementia rates varied only slightly according to the type of primary brain injury diagnosis, she said at a press briefing during the Alzheimer's Association International Conference on Alzheimer's Disease:

Concussion: 11.6%

Skull fracture: 14.9%

Post-concussion syndrome: 15.6%

Intracranial injury: 15.7%

Unspecified head injury: 16.0%

Overall: 15.3%

Yaffe and colleagues analyzed records of 281,540 veterans 55 and older with at least one visit to a VA medical facility during each of two periods: a baseline interval from 1997 to 2000 and a follow-up period of 2001 to 2007 -- thus providing seven years of follow-up for those veterans included in the study. Individuals already diagnosed with dementia as of the baseline period were excluded.

The researchers looked for diagnoses of TBI during the baseline period, and then for diagnoses of dementia during the follow-up interval, in both cases using the relevant ICD-9 codes in the veterans' records.

About 4,900 of the sample (1.7%) had received a TBI diagnosis during the baseline interval, Yaffe said.

After adjusting for demographic factors and comorbidities including post-traumatic stress disorder, the hazard ratio for a dementia diagnosis associated with previous TBI was 2.3 (95% CI 2.1 to 2.5).

Yaffe said that several mechanistic explanations for the relationship were possible.

One is that diffuse axonal injury caused by shearing forces could, over the long term, lead to cognitive decline. Another is that the injury triggers accumulation of beta-amyloid plaques and neurofibrillary tau tangles.

Other research has found beta-amyloid plaques in 30% of patients with a TBI history, Yaffe noted.

Still other factors could be simple neuronal death and/or inflammation and cytoskeletal pathology resulting from the injury, she said.

Yaffe suggested the public health consequences could be enormous, insofar as some 1.7 million civilian incidents of TBI occur in the U.S. annually, and troops serving in Afghanistan and Iraq have been suffering head injuries at high rates.

TBIs account for some 22% of all casualties in those conflicts and 59% of injuries sustained in explosions, Yaffe noted.

William Thies, PhD, chief medical and scientific officer of the Alzheimer's Association, who moderated the press briefing, told MedPage Today that the study was especially important because the sample was representative of the general older-male population in most respects.

"It probably is a group that looks like the rest of us," he said. "I think it gives us more insight into the risk any of us would have with head injury related to [subsequent] dementia."

Thies said it highlighted the importance of injury prevention -- specifically focusing on falls in older adults, who are most at risk for dementia.

The study was funded by the Department of Defense.

Yaffe and Thies had no disclosures.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

MedPageToday is a trusted and reliable source for clinical and policy coverage that directly affects the lives and practices of health care professionals.

Physicians and other healthcare professionals may also receive Continuing Medical Education (CME) and Continuing Education (CE) credits at no cost for participating in MedPage Today-hosted educational activities.